President Bush has declared war on the terrorists who perpetrated the outrages in the United States.

Here in the UK, Prime Minister Tony Blair has said that we stand shoulder to shoulder with our American allies.

On Friday, parliament in London has been recalled, to debate the UK's response to the gravest threat to the free world since the second world war.

But how far should Britain's support for the United States go? Should Britain be urging restraint on America, or backing it to the hilt in any military action which might be taken?

The BBC's political correspondent, Nick Robinson, was joined by Plaid Cymru's Elfyn Llwyd, and shadow minister for trade and industry, Alan Duncan. They answered a selection of your questions about what role Britain should take.

Newshost: Welcome to this BBC News Online discussion about the parliamentary debate here at Westminster about the consequences - what flows from the terrible attacks in the United States. I am joined by two Members of Parliament: Elfyn Llwyd, who leads the Welsh Nationalist Group, the Plaid Cymru group here in the Westminster Parliament and Alan Duncan, Conservative spokesman on foreign affairs - just appointed within the last few hours.

We have had a lot of questions from people by e-mail concerned about the consequences of these attacks. The first comes from Richard Orley from South Hadley asks: Terrorism is any state and any person or group that can be anywhere at any time. Can you make the mistake of thinking - not on my land - as I once did. I have learnt the cold hard fact that if you hesitate or use restraint about this you die or cost others their lives. Will you make the same mistake?

Elfyn Llwyd: We are living, it has to be said, in a global village now and people are free to move from one part of the world to the next and frequently do. It's becoming a smaller planet to live on and clearly the presumption must be that there are terrorists - or potential terrorists - around us at this moment in time. We must guard against it and be ever more vigilant following what happened in New York and Washington.

Newshost: There is already a sense - Alan Duncan - it was mentioned in the debate - that perhaps this will have to change the way we do things in Britain. Peter Mandelson, the former minister, speaking about the need for identity cards in Britain - always resisted by civil libertarians.

Alan Duncan: I think the first step is to improve our intelligence and improve it around the globe. War and conflict used to be about insurrection or one country invading another. Now, dreadful conflict and a horrible atrocity like Tuesday's can be perpetrated by a very few people who come from nowhere to be seen and then disappear or are themselves killed. That makes the nature of the threat much more difficult to see and to police and to respond to. So what you need is really effective intelligence domestically in the United Kingdom. As Elfyn says, we are now a global village, we are a cosmopolitan capital city where many an Arab and foreigner will come and enjoy their life and hopefully help us enjoy ours. But we must appreciate that in amongst ordinary people who we see in the street, there can also be threats.

Newshost: Elfyn, do you feel comfortable when you hear the Home Secretary saying we are going to look again at identity cards, we need to think hard about this?

Elfyn Llwyd: I wouldn't dismiss it out of hand. I am personally not in favour of it for civil liberty reasons.

Newshost: And this doesn't change your mind? Because some are saying we have changed our minds.

Elfyn Llwyd: I think we need perhaps another debate and another look at it. Clearly it shouldn't be dismissed out of hand as previously it might have been.

Newshost: Do you think it has a role to play?

Alan Duncan: I think you are dwelling on the wrong thing here. What you are really looking at is movements of money, telephone calls, messages between people, the import of explosives and the purchasing of weapons and things like that, security checks at airports. Those methods actually are probably more effective than bringing in identity cards, although I can see the argument.

Elfyn Llwyd: I think Alan is right. During the debate I made the point - and many others did as well - that it is a cross-border thing. Terrorists tend to collaborate with each other. We need better understanding between the various security services and the sharing of good intelligence is vital.

Newshost: The Prime Minister, the leaders of the opposition parties too, went out of their way to say - look the enemy is Islamic fundamentalism not the Muslim community. We have a question from Paul O'Neil in Southampton that relates the question here at home. He asks: What's to be done when the leader of the UK Muslim Youth Organisation said on television last night that if the West attack Islamic terrorists the Koran tells every Muslim they must treat it as a personal attack and respond accordingly?

Alan Duncan: I think we have all got to be careful about our language and I would caution against the loose use of Islamic fundamentalism. As if to say that anyone who has fervent religious beliefs is necessarily a terrorist. As in Northern Ireland, someone who is a terrorist is not necessarily a fundamental Catholic. I think we have to be careful not to confuse religion with the acts of terrorists.

I would say to this Muslim youth leader - cool it and choose your words carefully so that we can actually have trans-global understanding and not ferment some kind of conflict at a difficult time like this.

Elfyn Llwyd: I think that's right. We are all going out of our way to ensure that Muslims are not picked on in this country as a way of reprisal. But the point is, this is the only group, as far as I know, who have voiced this kind of opinion. Other major Muslim groups in the UK have condemned the action and basically supported the Government's words in support of America.

But as Alan has said, we all need to watch our language but we also need to strive to ensure that we do live with each other and we don't end up at each other's throats in this way.

Newshost: What would you both say to someone who says that cool it isn't enough? We have laws against the incitement of racial hatred or the incitement of violence and some say, looking at this, why aren't they being used against these sorts of people?

Elfyn Llwyd: I think the first thing this would do with this young man is to make him a bit of a martyr. He would be a cause celebre and probably he'd be attracting a bit more support than he otherwise would. I trust that in the cold light of day he'll reflect carefully on what he has said and fall in line with the other major Muslim groups because we all need to live together. This is a global problem and saying this kind of thing is not going to help.

Alan Duncan: I agree. I don't like what he has said but we shouldn't lock him up. We should try and help him understand - tempers are frayed. What we need is leadership and responsibility and I would urge him to just step back from what he has said and reflect on what he has said.

Newshost: Is there any role though if people don't cool it, if they are advised, if they are still there - is there a role for saying actually there are limits to the tolerance of what we will allow people to say?

Elfyn Llwyd: There has to be and we have laws in place for that and if that point is reached we need to use those laws but I don't think it's been reached yet and I do hope that with a bit of commonsense and a bit of patience that we will not be seeing any more of this.

Newshost: Katherine Monroe from England asks: While the world does and should condemn this act of terrorism, no one is talking about the real issue such as addressing the causes of extremism. A show of strength as retaliation is what we expect from the US but it is probably the last thing they should do. How do you think this event can be constructively responded to?

Alan Duncan, the concern here is that there is not an underlying cause to the act but an underlying cause for the anger that supports the act.

Alan Duncan: I think we are all entitled to be outraged by what has happened in New York and in Washington. But I also think we have a duty to try and understand the feelings of people that live in the Arabian Gulf and the people who have been, in many respects, very hard hit by the need to contain the likes of Saddam Hussein after his invasion of Kuwait. So we also have a duty to understand - but to explain is not to excuse and what these people have done from their midst, we suspect, is something which has to be followed up and contained and controlled.

Newshost: Her question also says - is there a more constructive response that can be taken?

Elfyn Llwyd: I think there is and if you listen to what George Galloway said earlier on - whether you agreed or not - he is an expert on Middle East politics. He was saying there is a large number of grievances that need to be addressed that we in this country and other countries could be looking at now and addressing.

Also there was a single sentence in the Prime Minister's speech about the Middle East peace process and the need to restart that as it were. Clearly that is another issue. There are other things we need to do - there are more constructive things and we need to encourage dialogue and better understanding - that is the only way forward. As Churchill said - jaw, jaw - not war, war.

Alan Duncan: I think we also have to persuade a lot of people - particularly younger people - in countries in the Arabian Gulf that these people are not their friends. They are actually also their greatest enemies too and if there is a threat to them and whatever peace there is in their country - actually, these people threaten it.

Newshost: Robert Rosenberg in London asks: Do we not all have to now be more proactive against these militants? Perhaps it is now time for the likes of Jack Straw, the Foreign Secretary, to cease his criticism of Israel and its policies to search and destroy and obvious terrorists?

There will be plenty of Israelis who will listen to the words used by leaders like Tony Blair and say well that's what we are doing and yet we have been criticised for searching and destroying terrorists.

Elfyn Llwyd: Searching and destroying is fine if it is based on good evidence but I would prefer the rule of law at the end of the day. We do have, albeit in its infancy, an international criminal court - I would like to see that extended and strengthened. I also favour the idea put forward by a leading Conservative today about the UN Convention and wanting all countries to sign up to it. That's also a positive step. But I think in this day and age, rather than search and destroy - search, apprehend and put before a court - I think that's the way forward.

Alan Duncan: I certainly agree that in everything we do in reaction to this atrocity, we must set the highest possible standards for us and justice must be our first word - revenge must be way at the end of the alphabet.

Newshost: Do you think, just to conclude, that the words of solidarity that we have seen expressed on a hitherto unseen scale - the UN, Nato, the EU - will that solidarity last when it is not mere words, not motions that they are having to agree on but actions?

Elfyn Llwyd: If the actions are appropriate, if they are proportionate, if they are careful and we don't have this awful so-called collateral damage - in other words innocents being killed - then I think the coalition will stay together and I hope it will.

Alan Duncan: I think what people have to remember in so many of the difficult decisions in foreign affairs is that moral decisions that are taken are normally one shade of grey or another - they are rarely black and white and that makes them all the more moral in their nature and in their quality. Some leaders are going to have to take some very difficult decisions over the months ahead and then is when they need support.